//球体顶点坐标
attribute vec4 vPosition;
varying vec4 aColor;
uniform mat4 vMatrix;
void main(){
    gl_Position=vMatrix*vPosition;
    float vColor;
    if (vPosition.z > 0.0){
        vColor=vPosition.z;
    } else {
        vColor=-vPosition.z;
    }
    aColor = vec4(vColor, vColor, vColor, 1.0);
}